PROBLEM TO BE SOLVED: To provide a new arrangement for synchronizing a gradient generator by making a recompressed volume the same as a recompressed volume of a high pressure pump.
SOLUTION: A check valve is kept closed at an initial stage of a pumping stroke of a first piston by which fluid is compressed at a finite volumetric elastic module, and a second piston provides all flows at fixed rotation speeds. When pressure in a cylinder of the first piston reaches delivery pressure once, and a delivery check valve opens, a control system is changed over to a constant pressure control mode to maintain a flow rate at a fixed value. When the delivery check valve of the second piston is closed and pump control is returned to fixed rotation speed, constant pressure control is switched off again. Angular displacement making the control mode changeover effective is determined by monitoring delivery pressure, and storing a value of angular displacement at which the first-grade time differential of pressure is remarkably changed.
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